The Mathematics of User Experience

Ever used an app that made you want to throw your phone? Why did it trigger that emotion? Pain. That’s why.

Bad user experiences aren’t just bad, they’re painful.

MEASURING PAIN

Whether you call something “bad” or “painful”, those are just words — what’s the difference? The difference is this: “bad” is subjective; “pain” is measurable.

How do you measure pain? Using what I call “pain points”. Pain points come in a few flavors:

Number of seconds to accomplish goal

Number of taps/clicks/actions to accomplish goal

Number of decisions needed to accomplish goal

Etc…

My favorite video game takes 12 steps just to start playing… Ouch.

These pain points will count differently for different people (depending on their patience, decision-fatigue, etc…), but fewer pain points will always be better. Maybe there are some UX S&M fans who like painful experiences, but I wouldn’t worry about those.

FORMULA FOR PAIN

What do all those symbols mean?

These are are the pain points — the primary inputs, which determine total pain.

The functions f, g, and h determine how much a particular user (u) is affected by each of those different types of pain points (e.g. monks can tolerate waiting, CEOs can tolerate decision making, …).

This theory of pain assumes that each of those functions is a monotonic function; that means, while twice as many pain points may not be twice as bad, it will be worse (or just as bad).

Given that assumption, even though you don’t know precisely how much each person cares about each type of pain point, you do know that you’ll give them a better experience by reducing pain points.

CONLUSION

You can think of pain points as a type of currency that a user pays to accomplish their goals. When a product’s UX is too painful, they will be “priced out”, and stop using it. To avoid this, minimize your pain points.